What is a key difference between PWRs and BWRs?

The key difference highlighted in the context of pressurized water reactors (PWRs) and boiling water reactors (BWRs) is that PWRs utilize steam generators and a pressurizer. In a PWR, water is used as both a coolant and a neutron moderator, and it is kept under high pressure to prevent it from boiling within the reactor core. The heated water from the reactor then flows through steam generators where it transfers heat to a secondary water loop, allowing steam to be produced that drives the turbines. The pressurizer plays a critical role in maintaining the pressure of the primary coolant system, ensuring that the water remains in a liquid state and effectively transfers heat.

This setup is essential for PWRs and differs significantly from BWRs, where water boils directly in the reactor core, generating steam that is directly used to turn the turbines. The design and operational protocols of these two reactor types reflect fundamental differences in how they manage heat transfer and pressure within the system, leading to distinct reactor designs and efficiencies.